A metal sphere cools at the rate of 1.5^ C / min when its temperature is 80^ C . At what rate will it cool when its temperature falls to 50^ C . [Temperature of surrounding is 30^ C ]

Step-by-step solution

When temperature is 80^ C , by Newton's law of cooling, we have 1.5= k ( 80+30 2 -30 )= k (55-30)=25 ~K When temperature is 50^ C , let r be the rate of cooling. Then aligned & r = k ( 50+30 2 -30 )= k (40-30)=10 ~K & r 1.5 = 10 25 & r =0.6^ C / min aligned